This invention relates to a network system and in particular to fault recovery in communication control units.
When a fault occurs in the D-plane in a generalized multi-protocol label switching (GMPLS) network, the path is switched in the optical switching unit in order to restore operation, and the path setup is reported to GMPLS control device. In one proposed protection method, the GMPLS control device utilizes a GMPLS signaling protocol at this time to notify all control devices that the path was switched and restore operation (refer to JP 2003-318983 A).
In another proposed method called the Graceful Restart method, when restarting after a fault has occurred, the GMPLS control device receives preexisting path information from other adjacent nodes to restore the path status to restore operation without terminating a path (refer to L. Berger, “GMPLS RSVP-TE” RFC 3473, IETF, January 2003).